Zak Hardaker, the Leeds and England full-back, is in danger of a lengthy suspension after the Rugby Football League set up an investigation into an allegation that he called James Child, the referee for last Friday’s Super League defeat at Warrington, a “fucking fag”.

The governing body issued a statement on Monday confirming that “an allegation that Zak Hardaker of Leeds Rhinos made homophobic comments has been referred to the RFL compliance department, which has begun a formal investigation”.

Both the RFL and Leeds have stressed a zero-tolerance attitude to homophobia in recent years. The RFL’s equality and diversity manager, Sarah Williams, received an MBE last June while the Rhinos wore the Stonewall logo on their kit in a 2012 fixture against Widnes – in which Hardaker scored two tries – in order to promote awareness of LGBT issues.

In June 2010 Castleford were fined £40,000 after Gareth Thomas, the Wales international then playing for the Crusaders, received homophobic abuse at their ground, but no Super League player has previously been charged.

Hardaker has been one of the outstanding players of the Super League season. He responded positively to being fined and publicly humiliated by Leeds last November after his withdrawal from England’s World Cup squad for “personal reasons”, which he later admitted were related to a breach of the squad’s drinking ban.

His case will not be heard until next week but there is thought to be a possibility that the controversy will cost him a place in the 35-man England training squad for the end-of-season Four Nations series in Australia and New Zealand, which will be announced on Tuesday.

Child, a 30-year-old from Leeds, has been a member of the RFL’s panel of full-time referees since 2010. He made his professional debut at 22 and took charge of his first Super League game at 25. He started refereeing in Dewsbury aged 11 and remains the youngest official to have been involved in a Challenge Cup, having been a touch judge at Wembley in 2006, aged 23.